全文获取类型
收费全文 | 1726篇 |
免费 | 124篇 |
国内免费 | 317篇 |
专业分类
安全科学 | 200篇 |
废物处理 | 61篇 |
环保管理 | 154篇 |
综合类 | 918篇 |
基础理论 | 289篇 |
污染及防治 | 307篇 |
评价与监测 | 73篇 |
社会与环境 | 109篇 |
灾害及防治 | 56篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 56篇 |
2021年 | 60篇 |
2020年 | 55篇 |
2019年 | 51篇 |
2018年 | 55篇 |
2017年 | 52篇 |
2016年 | 51篇 |
2015年 | 88篇 |
2014年 | 94篇 |
2013年 | 131篇 |
2012年 | 121篇 |
2011年 | 161篇 |
2010年 | 125篇 |
2009年 | 118篇 |
2008年 | 134篇 |
2007年 | 138篇 |
2006年 | 135篇 |
2005年 | 110篇 |
2004年 | 74篇 |
2003年 | 68篇 |
2002年 | 58篇 |
2001年 | 50篇 |
2000年 | 35篇 |
1999年 | 32篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 4篇 |
排序方式: 共有2167条查询结果,搜索用时 125 毫秒
571.
572.
Renyan Duan Chao Wang Xiao-an Wang Zhihong Zhu Hua Guo 《Russian Journal of Ecology》2009,40(7):501-509
We compared differences in plant species diversity between conifer (Pinus tabulaeformis) plantations and natural secondary forests in the middle of the Loess plateau. The goal of the study was to examine the differences
in the effect of stand development on species diversity and in species responses to changes between forest types and between
forest layers. To clarify the effects of differences in forest management, we emphasized the functional types of plant species
occurring in each forest type. The result as follow: (1) The H′ and S of tree layer were significantly lower in natural conifer forest than old conifer and secondary forest, but were not different
compared with mid aged conifer forest. The H′ and S of shrub layer were significantly lower in mid aged conifer forest compared with other forest types. The H′ of herb layer showed no significant differences in the four forest types. The evenness index (J′) of tree layer of mid aged conifer forest was lower than other forest communities and its J′ of shrub layer was highest although its richness of shrub layer was lower than in the other forest types. (2) The analysis
of β diversity index also indicated large differences between conifer plantations and natural forests. Although the tree layer
species were similar in old plantation and natural conifer forests, they differed greatly between the natural conifer and
secondary forests. The natural conifer and secondary forest species composition in shrub layer differed significantly from
those in plantation and secondary plots. Tree species were significantly less common in plantations than in abandoned coppice
forests. Species composition in the herb layer of different forest types was similar. (3) The management of P. tabulaeformis plantations alters plant species composition considerably; the number of sub tall-tree species is increased in old aged conifer
forest, especially species dispersed by animals. Plantation management appears to affect ecological processes through seed
dispersal. From the perspective of management, the change in the structure and composition of the canopy in plantations could
affect the behavior of dispersers and regeneration. 相似文献
573.
氯氰菊酯降解菌CY22-7的分离鉴定及降解特性研究 总被引:3,自引:1,他引:2
从采集的多种土壤样品中.获得了19株在3种筛选平板上均生长良好的候选氯氰菊酯降解菌.通过生理生化特性鉴定和16S rDNA序列的测定及比对.将其中的氯氰菊酯降解菌CY22-7鉴定为中华根瘤菌属(Sinorhizobium sp.).同时,对氯氰菊酯降解菌CY22-7的降解特性研究结果表明:(1)氯氰菊酯降解菌CY22-7以5%(体积分数)的接种鼍接种到氯氰菊酯起始质量浓度为100 mg/L的氯氰菊酯乙醇培养基后,于200 r/min、30℃摇床中培养.经过6 d的培养,氯氰菊酯降解菌CY22-7降解了约60%的氯氰菊酯.(2)加人外源营养物质有利于促进氯氰菊酯的降解.其中,葡萄糖和酵母提取物的促进作用最为明显.(3)氯氰菊酯降解菌CY22-7降解氯氰菊酯的最适温度为30℃,最佳pH为6.0. 相似文献
574.
渗透性能是化学防护服最重要的防护性能指标之一。本文采用PTC200型渗透测试池、蠕动泵、超滤装置和离子色谱分析仪,构建了测试化学防护服渗透性能的装置,并利用该装置对一系列化学防护服面料对浓硫酸和NaOH溶液的渗透性能进行了检测。结果表明,利用该装置可以方便准确地实现服装面料渗透性能测试,是一种具有重要应用价值的检测方法。该方法的开发为规范我们国家化学防护服装及相关产品防护性能检测方式,提高检测结果的准确度和一致性,具有重要的意义。 相似文献
575.
本文在对当前爆炸性气体环境的危险区域划分存在的主要问题及其原因分析的基础上,探讨了通过建立爆炸性气体环境危险区域计算机辅助划分平台,提高危险区域划分的可操作性,从而实现爆炸性气体环境危险区域划分方法的改善.探讨了通过运用数值计算方法,基于fluent对爆炸性气体扩散进行研究,对非对称分布场所的危险区域划分提供划分辅助. 相似文献
576.
ASE萃取-SPE净化-气相色谱法测定土壤中有机氯农药 总被引:6,自引:0,他引:6
建立了加速溶剂萃取-固相萃取净化-气相色谱测定土壤中α-六六六、β-六六六、γ-六六六、δ-六六六、P,P′-DDE、P,P′-DDD、O,P′-DDT、P,P′-DDT等8种有机氯农药的方法。在0μg/L~500μg/L范围内方法线性良好,8种有机氯农药的检出限在0.06μg/kg~0.21μg/kg之间,基质加标试验的相对标准偏差为2.2%~5.8%,回收率为81.5%~113%。 相似文献
577.
This paper developed an approach by the synthesis of remote sensing, landscape metrics, and statistical methods to examine the effects of landscape pattern, land surface temperature, and socioeconomic conditions on the spread of West Nile virus (WNV) caused by mosquitoes and animal hosts in Chicago, USA. Land use/land cover and land surface temperature images were derived from Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer imagery. An analytical procedure using landscape metrics was developed, applying configuration analysis of landscape patterns in the study area. The positive reports of mosquitoes and animal hosts for WNV in fall, 2001–2006, were collected from the Cook County Public Health Department. Forty-nine municipalities were found to have WNV-positive records in mosquitoes and animal hosts in fall 2004. Socioeconomic data were obtained from the 2000 US Census. Statistical analysis was applied to WNV data in fall 2004 to identify the relationship between potential predictors and WNV spread. As a result, landscape factors, such as landscape aggregation index and the urban areas and areas of grass and water, showed strong correlations with the WNV-positive records. Socioeconomic conditions, such as the population over 65 years old, also showed a strong correlation with WNV-positive records. Thermal conditions of water showed a less but still considerable correlation to WNV-positive records. This research offers an opportunity to explore the effects of landscape pattern, land surface temperature, and socioeconomic conditions on the spread of WNV caused by mosquitoes and animal hosts. Results can contribute to public health and environmental management in the study area. 相似文献
578.
在求取襄阳中心城区重现期雨量与可抽排雨量的基础上,采用基于GIS暴雨洪涝淹没模型计算不同重现期致灾雨量的淹没水深和范围;依据城市内涝对道路的实际影响,制作城市道路内涝灾害风险区划图。结果表明,该方法能够直观表达研究区域内不同雨量阈值的内涝灾害淹没风险分布,定量评估淹没水深、淹没范围。同时给出了城市道路内涝灾害风险区划图,结合城市道路信息,准确定位高风险易涝街区,为政府部门决策提供科学依据。 相似文献
579.
外部性与公共产品是环境规制的理论基础,以此为基点各国实行了包括税收、补贴、市场交易、行政强制等在内的多种规制政策,各种政策具有不同的作用机制和政策效果,需据实选择。我国现行的环境公共规制体系存在一定的缺陷。主要表现在4个方面:公共规制手段过手单一,政策效果难以保证;环境保护收费制度不完善。政策效果受限;环境保护税制不健全,导向作用不突出:排污权交易制度尚处手试点阶段,作用空间太小。为了有效实现环境保护目标,需要进一步构建并不断加以完善多元化的环境公共规制体系,即:改革环境收费制度,加强资金管理;完善现行税制,发挥税收的环保导向与激励作用;综合利用财政激励机制,扶持环境保护产业的发展;建立排污权交易市场,全面推行排污交易制度。 相似文献
580.
安全生产责任制度,是现代企业工程施工安全生产工作的基本制度,是落实企业安全生产主体责任、规范安全管理流程的基本法则。每一个建筑施工企业都会制定出从企业董事长、总经理到各个管理岗位,直到基层作业人员的安全生产责任制。在施工现场安全生产工作中,工程技术人员的安全责任落实是安全管理链条的重要环节。 相似文献